import java.util.Scanner;

public class demo5 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        int n=scanner.nextInt();
        StringBuilder stringBuilder=new StringBuilder();
        while (n>0){
            stringBuilder.append("A"+(--n)%26);
            n/=26;
        }
        System.out.println(stringBuilder.reverse());
    }
}
